The field of the invention relates generally to rotary blade systems, and more specifically, to methods and system for wirelessly balancing rotor assemblies.
Known gas turbine engines include rotor assemblies that are rotatable relative to stationary engine structures. Known rotor assemblies include a number of rotatable components including a central shaft, shaft cones, compressor blades and disks, turbine buckets and wheels, and/or dynamic air seals. Each component is acted upon by static and/or dynamic axial pressure forces. Rotor imbalance may be a common source of vibration in known rotor assemblies. An imbalance in rotary machinery may be evident if the mass axis of a rotating disk or shaft does not substantially coincide with the axis of rotation. In such operating conditions, the rotating shaft or disk rotates about its axis and generates a centrifugal force that is substantially distributed to the bearings and support structure. The centrifugal force may induce a vibrational frequency to the non-rotating structure that is synchronous with rotor speed. The resulting dynamic response of the rotor/stator system may cause amplitudes of motion or may lead to failure of the rotor, bearings, and/or the support structure.
To reduce the effects of imbalances, at least some known turbofan engines are manually balanced. In such a process, the fan assembly is balanced by coupling weights in the fan spinner or an adjacent rotating structure in an attempt to counter the rotor imbalance and to reduce the forced response of the system to acceptable levels. Vibration measurements are taken and used to calculate the distribution (amplitude and phase) of the corrective weights to be installed. The engine is then stopped and the appropriate weight(s) are added to the appropriate rotor assembly component. The engine is then cycled over its full rotor operating range to determine if the corrective weights reduced the vibration levels to acceptable levels. If the vibration levels are not acceptable, the process is repeated until acceptable vibration levels are achieved. Such a balancing procedure may be a time-consuming process that may require cycling the engine through its full rotor operating range several times. Additionally, balancing the fan assembly in this manner requires experienced technicians, expends significant quantities of fuel, and may result in an increase of environmentally undesirable emissions based on the increased engine running time.